None at all

Seller: How about some chicken wings or chicken legs or chicken breast?
Which would you like?
Man: Wings, legs, breast. No, none of them, thank you.
Seller: Do you want any meat or don't you?
Man: I don't want any meat.
Seller: None at all?
Man: No, none at all.
Seller: Why not? Don't you like meat?

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What does "None at all" mean?

Thank you